Pressure-sensitive copying paper containing lactone compound of pyridine carboxylic acid

ABSTRACT

A pressure-sensitive copying paper comprising an adsorbent solid acid and a microencapsulated color former capable of forming a destinct color when reacted with the adsorbent acid coated on the same or a different surface of a support or supports, the microencapsulated color former being at least one lactone compound derived from a pyridine-carboxylic acid represented by the formula;   or a mixture thereof, wherein A, A&#39;&#39; and Y are as defined hereinafter, is disclosed.

United States Patent [1 1 Ozutsumi 'et al.

[451 Oct. 28, 1975 PRESSURE-SENSITIVE COPYING PAPER CONTAINING LACTONE COMPOUND OF PYRIDINE CARBOXYLIC ACID [75] Inventors: Minoru Ozutsumi; Yoshihide Miyazawa; Katsuichi Motohashi; Taiji Watanabe, all of Tokyo; Sadao Ishige, Kanagawa; Keiso Saeki; Akio Watanabe, both of Shizuoka, all of Japan [73] Assignees: Hodogaya Chemical Co., Ltd.,

Tokyo; Fuji Photo Film Co., Ltd., Minami, Ashigara, both of Japan [22] Filed: Mar. 15, 1974 [21] Appl. No.: 451,400

[30] Foreign Application Priority Data Mar. 15, 1973 Japan 48-29468 [52] U.S. Cl 428/411; 260/243; 260/279 R; 260/287 P; 260/287 T; 260/294.8 C; 260/295 [51] Int. C15... B41C 1/06; B41M 5/14; 1341M 5/16 [58] Field of Search 117/362, 36.4, 36.8, 36.9; 260/295 R, 296 H [56] References Cited UNITED STATES PATENTS 3,703,397 11/1972 Lin et al. 117/362 3,736,168 O zutsumi et al 117/362 5/1973 ll/l973 Primary ExaminerP. E. Willis, Jr. Attorney, Agent, or FirmSughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT or a mixture thereof, wherein A, A' and Y are as defined hereinafter, is disclosed.

2 Claims, No Drawings Farber 260/295 B 1 PRESSURE-SENSITIVE COPYING PAPER CONTAINING LACTONE COMPOUND OF PYRIDINE CARBOXYLIC ACID- BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive copying paper using as a color former a pyridinecarboxylic acid lactone represented by the following general formula;

or a mixture thereof, wherein A and A, which may be the same or different, each-represents a pyrrolyl, indolyl, carbazolyl, acridinyl, phenothiazinyl, thienyl, thianaphthenyl, julolidinyl or tetrahydroquinolyl group and Y represents a hydrogen atom, a lower alkyl group having 1 to 4 carbon atoms, a halogen atom or a phenyl group, with the proviso that A and A both cannot simultaneously be an indolyl group or a pyrrolyl group.

2. Description of the Prior Art In general, pressure-sensitive copying paper comprises the combination of an upper sheet (or transfer sheet) having coated on the back surface thereof minute microcapsules containing dissolved therein an electron donative substantially colorless organic compound capable of undergoing color reaction, i.e., color former, and a lower sheet paper (or receiving sheet) having coated on the surface thereof a color developer. When these two coated surfaces are brought into contact with each other and a localized pressure is applied to the assembly by handwriting or typewriting, microcapsules located at the pressure-applied area rupture and the organic color former contained in the organic solvent comes into contact with the color developer to form color.

Pressure-sensitive copying paper systems comprising the aforesaid transfer sheet and a receiving sheet and an intermediate sheet are also known. In these systems the middle sheet is usually coated, on opposite surfaces, with a layer of micro-capsules containing a color former solution and with a layer of a solid acid and a stances such as acid clay, attapulgite, zeolite, bentonite; solid organic acids such as succinic acid, tannic acid, benzoic acid; and acidic polymers such as phenolformalin polymer, phenol-acetylene polymer, residual acid group-containing styrene-maleic anhydride polymer, salicylic acid-formalin polymer.

As the organic solvent for dissolving the color for mer, there are, such as ethylene glycol, chlorobenzenes, diphenyl ,chloride diethyl phth'alateitrioctyl phosphate, alkylnaphthalenes and naphthylalkyl alcohols.

SUMMARY OF THE INVENTION As a result of detailed investigations on the color former for pressure-sensitive copying paper, the present inventors have discovered that there can be obtained a pressure-sensitive copying paper capable of forming an orange, red, purple, blue, green or alike color by using as a color former a novel pyridine-carboxylic acid lactone represented by the above formula (I), and that there can be obtained a pressure-sensitive copying paper capable of forming optional desired color by using the novel color former in combination with a known color former or formers.

DETAILED DESCRIPTION OF THE INVENTION Pressuresensitive copying papers using the novel pyridine-carboxylic acid lactone represented by the formula (I) is colorless or slightly colored before color reaction, but, when in contact with the color developer, it immediately forms orange, red, purple, blue, green or a like color with high color density.

The thus formed color is excellent in light resistance.

On the other hand, pressure-sensitive copying paper using the novel color former in combination with a known color former or formers immediately forms an optional color when brought into contact with the color developer. The thus formed color undergoes little change in hue with the lapse of time after color formation.

Now, representative examples of the color former, pyridine-carboxylic acid lactones represented by the formula (I) to be used for the pressure-sensitive copying paper of the present invention are given below.

Color Former Chemical Term of Color Former Color Former -Continued Chemical Term of Color Former Nov A general process for producing pyridine-carboxylic acid lactones is described below.

1. First, the starting material, pyridine-carboxylic acid, is produced as follows. 1.0 M01 of quinolinic anhydride represented by the following formula;

whereiri Y is the same as defined in the formula (I) is reacted with 1.0 to 2.0 mols of a heterocyclic compound represented by the following formula;

(111) wherein A is the same as defined in the formula (I), in l to 2.5 l of a volatile organic solvent such as carbon disulfide, tetrachloroethane, benzene, nitrobenzenes, or the like at a temperature of 10 to C for l to 9 hours with 1.0 to 3.0 mols of a Friedel-Crafts catalyst such as zinc chloride or aluminum chloride.

Thereafter, the reaction mixture is cooled to room temperature and the above-described inert solvent is removed by decantation.

The resulting reaction product is poured into 2 to 6 l of ice-water or cold dilute aqueous hydrochloric acid to hydrolyze the catalyst. The precipitated solid is collected by filtration, washed successively with water and an alcohol or benzene. After drying, there is obtained an isomer mixture comprising a 2-(heterocycliccarbonyl)-pyridine-carboxylic acid-(3) represented by the following formula;

COOH

A-CO

wherein A and Y are the same as defined in the formula (I) and a 3-( heterocyclic-carbonyl)-pyridinecarboxylic acid-(2) represented by the following formula;

COOH

A-CO (V) wherein A and Y are the same as defined in the formula lf necessary, the above obtained isomer mixture may be separated into each of the isomers thereby obtaining a highly purified Z-(heterocyclic-carbonyl)-pyridinecarboxylic acid-(3) or 3-(heterocyclic-carbonyl)-pyridine-carboxylic acid-(2), or (heterocyclic-carbonyl)- pyridine-carboxylic acids in which two isomers are present in various proportions can be obtained by 1) dissolving the mixture in dilute aqueous sodium hydroxide. adding dilute aqueous hydrochloric acid to the resulting solution in small portions and recovering each of solids which separately precipitates due to the difference in pH or (2) repeatedly recrystallizing the mixture using a mixture of a less polar solvent such as benzene, toluene and the like and a polar solvent such as methanol, butanol and the like or (3) a combination of (l) and (2) above.

2. A pyridine-carboxylic acid lactone represented by the above formula (I) is produced as follows. 1.0 MOI of a mixture of isomers represented by the formulae (IV) and (V) and 0.9 to 1.5 mols of a heterocyclic compound represented by the formula (III) are added to concentrated sulfuric acid, acetic anhydride or polyphosphoric acid, and the reaction mixture is heated to a temperature of 50 to 130C for 2 to hours followed by cooling to room temperature. Then, the reaction product is poured into ice-water followed by adding thereto a dilute aqueous solution of sodium hydroxide to make the solution weakly acidic or neutral. To this is then added benzene, toluene or the like followed by stirring to transfer any unreacted heterocyclic compound to the benzene, toluene or a like layer. Then, the benzene or toluene layer is separated off. To the resid-' ual solution is added dilute. aqueous sodium hydroxide to adjust the pH to 11 to 12. The precipitated solid is filtered off, washed successively with water and a small amount of analcohol or benzene. v

After drying, there is obtained a substantially colorless or slightly colored pyridine-carboxylic acid lactone represented by the formula (I) corresponding to the mixture of isomers represented by the formulae (IV) and (V) in high yield. Or else, after adding a dilute aqueous sodium hydroxide to the residual solution to adjust the pH to 1 l to '12, benzene or toluene is added thereto followed by stirring to thereby transfer pyri-.

dine-carboxylic acid lactone to the benzene or toluene I layer. Then, the benzene or toluene layer is separated out, and benzene or toluene is distilled off. The thus obtained residue is washed successively with water and a small amount of an alcohol or'benzene.

After drying, there is obtained in high'yield a substantially colorless or slightly colored pyridine-carboxylic:

acid lactone represented by the-formula (I)'corresponding to the mixture of isomers represented by the formulae (IV) and (V) used as the starting material. If necessary, the thus obtained pyridine-carboxylic acid lactone'may be recrystallized.

The process for the production of the color former,

' pyridine-carboxylic acid lactone,.according to the present invention will now be illustrated by reference to the following Examples.

PREPARATION EXAMPLE 1 (Color Former Nos. 1

and 2) 30 g of quinolinic anhydride and 75 g of 9- ethylcarbazole were added to 300 ml of benzene, and

i 80 g of anhydrous aluminum chloride was added to the hours and thereafter cooled to room temperature. The

benzene layer was removed by decantation, and the resulting reaction product was added to 2 l of a cold 2N aqueous hydrochloric acid followed by stirring. The" I precipitated solid was recovered by filtration, washed with water and then a small amount of ethanol and dried to obtain 48.1 g of an isomer mixture comprising 2-[9-ethylcarbazole-carbonyl-( 3 -pyridine- Carboxylic acid-(3) and 3- [9'-ethylcarbazole-carbonyl- (3)]-pyridine-carboxylic acid-(2) as pale brown crystals having a melting point of 155 to 167C.

40 g of the isomer mixture thus obtained (m.p., 155 to 167C) was then dissolved in dilute aqueous sodium hydroxide, and the resulting solution was adjusted to a pH of6 with dilute aqueous hydrochloric acid. The precipitated solid was filtered (the filtrate was set aside), washed with water and dried to give 28 g of an isomer mixture comprising predominantly 3-[9- ethylcarbazole-carbonyl-( 3 -pyridine-carboxylic acid-(2) and a small amount of 2-[9'-ethylcarbazolecarbonyl-(3)]-pyridine-carboxylic acid-(3) as pale brown crystals having a melting point of 202 to 212C. Several recrystallizations of 20 g of the above obtained crystals from a mixed solvent of benzene-methanol (1:1 by volume) gave 12.5 of a highly purified 3-[9- ethylcarbazole-carbonyl-( 3 ]-pyridine-carboxylic acid-(2) as substantially colorless crystals having a melting point of 215 to 217C.

On the other hand, to the filtrate having a pH of 6 obtained from the above filtrationwas added dilute aqueous hydrochloric acid to adjust a pH to about 2. The precipitated solid was filtered, washed with water and dried to obtain 1 1.3 g of an isomer mixture comprising predominantly 2-[9'-ethyl-carbazole-carbonyl-(3")1- pyridine-carboxylic acid-(3) and a small amount of 3- [9 '-ethylcarbazole-carbonyl-( 3 ]-pyridine-carboxylic acid-(2) as pale brown crystals having a melting point of 156 to 162C. 10 g of the isomer mixture thus obtained was then recrystallized several times using a mixed solvent of toluene-ethanol (1:1 by volume) to give 3.7 g of a highly purified 2-[9'-ethylcarbazolecarbonyl-(3')]-pyridine-carboxylic acid-(3) as pale yellow crystals having a melting point of 165 to 167C.

3.7 g of the above obtained 2-[9'- ethylcarbazolecarbonyl-( 3 )]-pyridine'-carboxylic acid- (3) (m.p., 165 to 167C) and 1.6 g of 1,2- dimethylindole were added to 30 g of acetic anhydride and the mixture was allowed to react at a temperature of 120 to 125C for 3 hours and thereafter cooled to room temperature. The reaction product was poured into 300 g of 'ice-water to hydrolyze the acetic anhydride while stirring. After completion of hydrolysis, 5O

ml of benzene was-added thereto. The aqueous layer of the mixture was adjusted to a pH of 6.5 with dilute aqueous sodium hydroxide to transfer any unreacted. 1,2-dimethylindole to the benzene layer, which was. 1 then removed by separationQThe residual aqueous solution was adjusted to a pH of 12 with dilute aqueous sodium hydroxide and the precipitated solid was recovered by filtration, washed successively with water and a small amount of ethanol and dried. There was obtained 3.8 g of a compound (color former No. 1) represented by the formula;

as slightly pale yellow-colored crystals having a melting point of 198 to 199C.

2.5 g of the above obtained 3-[9'- ethylcarbazolec arbonyl-( 3 )]-pyridine-carboxylic acid- (2) (m.p., 215 to 217C) and 1.1 g of 1,2- dimethylindole were added to 20 g of acetic anhydride, and the mixture was allowed to react at a temperature of 120 to 125C for 4 hours followed by cooling to room temperature. The reaction product was poured into 200 g of ice-water to hydrolyze the acetic anhydride while stirring. After hydrolysis, 40 ml of benzene was added thereto, and the aqueous layer of the resulting mixture was adjusted to a pH of 6.5 with dilute aqueous sodium hydroxide to transfer any unreacted 1,2-dimethylindole to the benzene layer. The benzene layer was removed by separation, and 50 ml of benzene was added to the solution. The aqueous layer of the resulting mixture was adjusted to a pH of 12 with dilute aqueous sodium hydroxide and the benzene layer was recovered by separation. The benzene was distilled off from the benzene layer and the residue was washed successively with water and a small amount of ethanol and dried to give 2.5 parts by weight of a compound (color former No. 2) represented by the formula;

as pale yellow-colored crystals having a melting point of 21 1 to 212C.

PREPARATlON EXAMPLE 2 (Color Former No. 3)

3.7 g of the isomer mixture of a pyridine-carboxylic acid obtained in Preparation Example 1 (m.p., 155 to 167C) and 1.6 g of 1,2-dimethylindole were added to 30 g of acetic anhydride, and the mixture was allowed to react at a temperature of 120 to 125C for 4 hours of 12 with dilute aqueous sodium hydroxide. The benzene layer was taken out by separation, and the benzene was distilled off from the benzene layer to obtain a residue, which was then washed successively with water and a small amount of ethanol and dried to give 3.9 g ofa mixture of isomers (color former No. 3) represented by the formulae;

I CH5 (H5 and l 1 N l 0:0 011 N CH5 as pale brown crystals having a melting point of 180 to 188C.

PREPARATION EXAMPLE 3 (Color Former Nos. 4

3.7 g of the same isomer mixture of a pyridinecarboxylic acid as used in Preparation Example 2 and the corresponding indole or 9-ethylcarbazole were added to 30 g of acetic anhydride. After completion of the reaction, the reaction product was worked up in the same manner as described in Preparation Example 2 to obtain a pyridine-carboxylic acid lactone, respectively, as crystals. The corresponding indoles or 9- ethylcarbazole, amounts of these reactants and reaction temperatures and periods as well as yields and melting points and crystal appearance of the resulting pyridine-carboxylic acid lactones are shown in Table 1 below.

Table 1 Color Corresponding lndole Reaction Reaction Yield M.P. Crystal Former or Carbazole and Temp. Time Appearance Amount Thereof (C) (hr) (g) (C) No. 4 l-Methyl-Z-phenyl- 2.1g 1 10-120 8 4.0 223-230 pale brown indole No. 5 l-Methyl-2-phenyl- 2.7g l20-l25 4 4.2 20l2l3 pale brown 4-chloroindole N0. 6 1.2,5-Trimethyl- 1.9g l 20-l25 4 3.9 178-185 pale yellow indole No. 7 l-Ethyl-Z-methyl- 2.3g -125 4 4.0 160-172 pale yellow S-mcthoxyindole No. 8 9-Ethylcarbazolc 2.1g 5 4.5 218-225 pale yellow followed by cooling to room temperature. The reaction 6 PREPARATION EXAMPLE 4 (Color Former No. 9)

3.0 g of quinolinic anhydride and 6.1 g of julolidine were added to 30 ml of benzene, and 8.3 g of anhydrous aluminum chloride was added to the mixture in small portions. After completion of addition, the mixture was allowed to react at a temperature of 45 to 50C for 3 hours followed by cooling to room temperature. The reaction product was worked up in the same manner as described in Preparation Example 2 to give 4.5 g of an isomer mixture comprising 2-[julolidinecarbonyl-(6')]-pyridine-carboxylic acid-(3) and 3- [julolidine-carbonyl-(6')]-pyridine-ca rboxylic acid-(2) as pale yellow colored crystals having a melting point of 228 to 239C.

3.5 g of the above obtained isomer mixture and 1.8 g of 1,2-dimethylindole were added to 20 g of acetic anhydride, and the mixture was allowed to react at a temperature of 105 to 110C for 2 hours. After completion of the reaction, the reaction product was 10 worked up in the same manner as described in Preparation Example 2 to obtain 3.8 g of an isomer mixture (color former No. 9) represented by the formulae;

as pale brown crystals having a melting point of 229 to 235C.

PREPARATION EXAMPLE 5 (Color Former Nos. 10

In the same manner as described in Preparation Example 1 except that l-methylpyrrole, acridine, phenoplace of 9-ethylcarbazole was reacted with quinolinic anhydride to prepare the following corresponding pyridine-carboxylic acid, respectively:

An isomer mixture comprising 2-[1-methylpyrrolecarbonyl-(2)]-pyridine-carboxylic acid-(3) and 3-H- methylpyrrole-carbonyl-(2)] pyridine-caraboxylic acid-(2);

An isomer mixture comprising Z-[acridine-carbonyl- (2)]-pyridine-carboxylic acid-(3) and B-[acridinecarbonyl-(2')]-pyridine-carboxylic acid-(2);

An isomer mixture comprising 2-[phenothiazinecarbonyl-(3)]-pyridine-carboxylic acid-(3) and 3- [phenothiazine-carbonyl-(3)]-pyridine-carboxylic acid-(2);

An isomer mixture comprising methylphenothiazine-carbonyl-(3')]-pyridinecarboxylic acid-(3) and 3-[10'-methyl-phenothiazinecarbonyl(3)]-pyridine-carboxylic acid-(2);

An isomer mixture comprising 2-(2-thenoyl)-pyridine-carboxylic acid-(3) and 3-(2'-thenoyl)-pyridinecarboxylic acid-(2);

An isomer mixture comprising Z-[thianaphthenecarbonyl-(2)]-pyridine-carboxylic acid-(3) and 3- [thianaphthene-carbonyl-(2)]-pyridine-carboxylic acid-(2); or

An isomer mixture comprising 2-[ l '-methyl-2,3,4- trihydroxyquinoline-carbonyl-(6')]-pyridinecarboxylic acid-(3) and 3-[] '-methyl-2',3',4'- trihydroxyquinoline-carbonyl-(6)]-pyridinecarboxylic acid-(2).

Each of the above obtained isomer mixtures was then reacted with the corresponding heterocyclic compound, and the reaction product was worked up in the same manner as described in Preparation Example 2 to obtain the corresponding pyridine-carboxylic acid lactone, respectively, as crystals. The corresponding pyridine-carboxylic acids and heterocyclic compounds used in this example and the melting points and crystal thiazine, IO-methyl-phenothiazine, thiophene, thia- 40 appearance of the resulting pyridine-carboxylic acid naphthene or l-methyl-2,3,4-trihydroquinoline in lactones are shown in Table 2 below.

Table 2 Color lsomer Mixture of Hetcrocyclic Melting Crystal Former Pyridine-carhoxylic Acid Compound Point Appearance (C) No. 10 2-[ l-Methylpyrrole-carhonyl- 9-Ethylcarbazole 'l2()l25 pale brown (2')l-pyridine-carboxylic acid- (3) and 3-1 l'-Methylpyrrolecarbonyl-(2')]-pyridinecarboxylic acid-(2) No. ll Z-lAcrydine-carbonyl-(2)]- 9-Ethylcarhuzole 240-247 pale brown pyridinecarboxylic acid-(3) and 3-[Acrydine-carbonyl-(2)1- pyridine-carboxylic acid-(2) No 12 2 [Acrydine-carbonyl-(2')]- Thianaphthene 228-235 pale yellow pyridine-carhoxylic acid-( 3) and 3 [Acrydine-carbonyl (2)]- pyridine-carboxylic acid(2) No 13 2-[Phenothiazine-earbonyl- 1,2-Dimethyl- 240245 pale brown (3')]-pyridine-carboxylic acidindole (3) and 3-[Phenothiazinecarbonyl-(3')]-pyridinecarboxylic acid-(2) No. 14 2-[ l0'-Methylphenothiazine- LZ-Dimethyl- -165 pale brown carbonyl-(3)]-pyridineindole carboxylic acid-(3) and 3-[ l0- Methylphenothiazine-carbonyl- (3 )-pyridine-carb oxylic acid- (2) No l5 2-(2'-Thenoyl)-pyridine- LZ-Dimethyl- 163-175 pale brown carboxylic acid;(3) and 3-(2- indole Thenoyl)-pyridine-carboxylic acid-( 2) T b e 2-continued Color lsomer Mixture of Heterocyclic Melting Crystal Former Pyridine-carboxylic Acid Compound 1: 2p; Appearance No. 16 2-lThianaphthene-carbonyl- 1,2-Dimethyl- 1 18-125 pale brown (2')] -pyridine-carboxylic acidindole (3) and 3-1ThianaphthenecarbOnyl-(Z'H-pyridinecarboxylic acid-(2) No. 17 2-1l'-Methyl-2'.3,4'-tri- 1,2-Dimethyl- 197-210 pale yellow hydroquinoline-carbnyl-(6')]- indole pyridine-carboxylic acid-(3) and 3-[ l-Methyl-2',3,4'-trihydroquinoline-carbonyl-(6)]- pyridine-carboxylic acid-(2) PREPARATION EXAMPLE 6 (Color Former No. 18) carboxylic acid-(3) and 3-[l',2'-dimethylindole- 1n the same manner as described in Preparation Ex- Carbonyl'(3I)1'4 chlom'pyridlne'carboxyllc acid'Q); ample 1 except that 3.3 g of 1,2,3,4- or I I tetrahydroquinoline in place of 9-ethylcarbazole was lsomer mlxturel compnsmg reacted with 3.0 g of quinolinic anhydride to prepare 20 dlmethyllndole'Farbonyl(3 f 'P 3.8 g of an isomer mixture comprising 2-[l,2,3,4'- carboxyhc acld'(3) and l tetrahydroquinoline carbonyl (6/)] Pyridine carbonyl-(3')]-6-phenyl-pyridme-carboxyllc acid-(2). carboxylic acid (3) and 2 Each of the above obtained isomer mixtures was then tetrahydroquinoline-carbonyl-(6)]-pyridi reacted with thiophene, and the reaction product was carboxylic acid-(2). 2.8 g of the thus obtained isomer Worked p in the same manner as described in p mixture and 2.0 g of phenothiazine were added to 20 {ion mp 2 t0 g the corresponding pyri e g f l h h i id, d th mi t r was all ed carboxylic acid lactone, respectively (color former to react at a temperature of 1 10 to 120C for 5 hours. Nos. 19-21 After completion of the reaction, the reaction product 1n order to produce pressure-sensitive copying pa was worked up in the same manner as described in pers using pyridine-carboxylic acid lactones repre- Preparation Example 2 to obtain 3.0 g of an isomer sented by the formula (1) as a color former, there may mixture (color former No. 18) represented by the forbe employed the methods well known in the art as demulae; scribed in U.S. Pat. Nos. 2,800,457 and 2,800,458, in which phenomenon of complex coacervation is utilized C S to produce microcapsules. Generally, the color former (n O I I: is used in an amount of 0.5 to 5.0% by weight based on N N O N the aforesaid organic solvent such as ethylene glycol, H H benzene chloride, diphenyl chloride, diethyl phthalate,

trioctyl phosphate, alkylnaphthalene, naphthylalkyl ald cohol, etc.

The pressure-sensitive copying paper using pyridinec s carboxylic acid lactone represented by the formula (1) (m Q I: will be now illustrated in greater detail by the following N l N non-limiting examples of preferred embodiments of the H I C O H present invention.

EXAMPLE 1 2.0 Grams of Color former Nos. l3 were taken up as pale yellow-colored crystals having a melting 130111t and treated as follows. Each color former was dissolved of to in 100 g of naphthylalkyl alcohol, and 20 g of gum ara- PREPARATION EXAMPLE 7 (Color Former bio and 160 g of water were added thereto at a temper- 19 21) ature of 50C to emulsify. To this emulsion were added 20 g of acid-treated gelatin and 160 g of water and, In the Same manner as described in Preparation under stirring, acetic acid was added thereto to adjust ample 2 except that 4'methyl'quihohhlc ahhydrlde, the pH to 5. Then, 500 g of water was added thereto to CHOW-quinolinic ahhydrlde or 'p y q allow coacervation to proceed. Thus, thick, liquid film hydride Place of the quinolinic ahhydride was of gelatin-gum arabic was formed around oil droplets acted with 1,2-dimethylind0le to p p the following of naphthylalkyl alcohol containing dissolved therein corresponding pyridine-carboxylic acid, respectively. th color fQnnef Af dj i h H to 4 4 4 g f An iSOmel miXture ompris g 2-[1',2'- a 37% formalin aqueous solution was added thereto to dimethylindole-carbonyl-(3)]-4-methyl-pyridineharden the above-described liquid film. Then, the syscarboxylic acid-(3) and 3-[1,2'-dimethylindoletem was cooled to 10C and, after adding thereto dilute carbonyl-(3')]-4-methyl-pyridine-carboxylic acid-(2); aqueous sodium hydroxide to adjust the pH to 9, it was An isomer mixture comprising 2-[1,2'- allowed to stand for 5 to 6 hours to thereby complete dimethylindole-carbonyl-( 3 -4-chloro-pyridineencapsulation.

The resulting microcapsule-containing liquid was applied to a paper by a coating method such as rollcoating, air knifecoating, etc. After drying, there was obtained a colorless coated paper (upper sheet paper). When this upper sheet paper was intimately superposed on a lower sheet paper having coated thereon an active clay'substance as a color developer and a localized pressure was applied to the assembly by handwriting, a purple color was immediately formed on the lower sheet paper at the pressed area. The color density of developed purple was high.

There was observed almost no discolorationand fading of the thus developed purple color even when it was exposed directly to sunlight for a long period of time.

Alternatively, when the upper sheet paper was intimately superposed on a lower sheet paper having coated thereon an acidic organic polymer and a localized pressure was applied thereto by handwriting, a bluish purple color was immediately formed on the lower sheet paper at the pressure-applied area.

EXAMPLE 2 2.0 Grams of color former No. 4 was taken up and treated in the same manner as described in Example 1.

After coating and drying, there was obtained a colorfor a long period of time. Alternatively, when the upper sheet paper was intimately superposed on a lower sheet paper having coated thereon an acidic organic polymer as the color developer and a localized pressure was applied to the assembly by handwriting, there was immediately developed a blue color on the lower sheet paper at' the pressed area. 7

EXAMPLE 3 2.0 Grams of color former Nos. l0 and 17 were taken up and each of'them was treated in the same manner as described in Example 1.

After coating and drying there was obtained colorless upper sheet papers. Each of the resulting papers was i lintimately superposed on alower sheet paper having coated thereon an acid clay substance as a color developer. When a localized pressure was applied to the assembly, a deep color image was immediately formed on the lower sheet paper at the pressed area. The image thus formed exhibited a sufficient stability to the lapse of time for practical use. The hues developed on the lower sheets are shown in Table 3 below.

EXAMPLE .4

2.0 Grams of color former Nos. ll-l2 and 18 were taken up and each of them was treated in the same manner as in Example 1.

After coating and drying, there were obtained upper sheet papers. When each of the resulting papers was intimately superposed on a lower sheet paper having coated thereon an acid clay substance as a color developer and a localized pressure was applied to the assembly by handwriting, there was immediately developed a deep color on the lower sheet paper at the pressed area. The thus developed color images showed sufficient stability for practical use. The hues developed on the lower sheets are tabulated below.

Table 4 Color Former Hue No. ll green No. 12 reddish orange No. 18 purple EXAMPLE 5 2.0 Grams of Color former 'Nos. 13-16 and l92l were taken, up and each of them was treated, coated and dried in the same manner as in Example 1. Thus, there were obtained colorless upper sheet papers. When each of the resulting papers was intimately superposed on a lower sheet paper having coated thereon an acid clay substance as a color developer and a localized pressure was applied to the assembly by handwriting, there was immediately developed a red color image on the lower sheet paper at the pressed area. Almost no discoloration orfading of the thus developed red color was observed even when it was exposed directly to sunlight for a long period of time. When this upper sheet paper was superposed on a lower sheet paper having coated thereon an acidic organic polymer as a color developer and a localized pressure was applied to the assembly by handwriting, there was immediately devel-" oped a red color on the lower sheet paper.

EX MPLE 6 23 Grams" of color former No. 3, 03 vg of ohydroxybenzalacetophenone, 0.l g of rhodamine B- anilinolactam, 0.1 g of malachite green'lactoneand 0.2

g of 'benzoyl leu co methyleneblue were treated and coated in the same manner as in Example 1 to prepare an upper sheet paper. When this upper sheet paper was superposed on a lower sheet paper having coated thereon an active clay substance as a color developer and a localized pressure was applied to the assembly by handwriting, there was immediately developed a black color on the lower sheet paper. The thus developed black color scarcely underwent change in hue and fad- While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made without departing from the spirit and scope thereof.

What is claimed is:

1. A pressure-sensitive copying paper comprising on a support a layer of an encapsulated color former and on the same or different support a layer of an electron 

1. A PRESSURE-SENSITIVE COPYING PAPER COMPRISING ON A SUPPORT A LAYER OF AN ENCAPSULATED COLOR FORMER AND ON THE SAME OR DIFFERENT SUPPOR A LAYER O AN ELECTRON ACCEPTING SOLID, SAID COLOR FORMER BEING A LACTONE COMPOUND DERIVED FROM A PYRIDINE-CARBOXYLIC ACID, REPRESENTED BY THE FORMULA
 2. The pressure-sensitive copying paper according to claim 1, wherein said color-former is a compound selected from the group consisting of: 2-( Alpha -(9''-ethylcarbazol-(3'')-yl)- Alpha -(1'', 2''dimethylindol (3'')-yl -methyl-pyridine-carboxylic acid-(3) lactone, 3-( Alpha -(9''-ethylcarbazol-(3'')-yl)- Alpha -(1'',2''-dimethylindol-(3'')-yl)- Alpha -oxy)-methyl-pyridine-carboxylic acid-(2) lactone, an isomer mixture comprising 2-( Alpha -(9''-ethylcarbazol-(3'')-yl)- Alpha -(1'',2''-dimethylindol-(3'')-yl)- Alpha -oxy)-methyl-pyridine-carboxylic acid-(3) lactone and 3-( Alpha -(9''-ethylcarbazol-(3'')-yl)- Alpha -(1'',2''-dimethylindol-(3'')-yl)-Alpha -oxy)-methyl-pyridine-carboxylic acid-(2) lactone, an isomer mixture comprising 2-( Alpha (9''-ethylcarbazol-(3'')-yl)- Alpha -(1'',2''-dimethyl-5''-methoxyindol-(3'')-yl)- Alpha -oxy)-methyl-pyridine-carboxylic acid-(3) lactone and 3(- Alpha -(9''-ethylcarbazol-(3'')-yl)- Alpha -(1'',2''-dimethyl-5''-methoxyindol-(3'')-yl)- Alpha -oxy)-methyl-pyridine-carboxylic acid-(2) lactone, an isomer mixture comprising 2-( Alpha , Alpha -di-(9''-ethylcarbazol- (3'')-yl)- Alpha -oxy)-methyl-pyridine-carboxylic acid-(3) lactone and 3-( Alpha , Alpha -di-(9''-ethylcarbazol-(3'')-yl)- Alpha -oxy)-methyl-pyridine-carboxylic acid-(2) lactone, an isomer mixture comprising 2-( Alpha -(1''-methylpyrrol-(2'')-yl)- Alpha -(9''-ethylcarbazol-(3'')-yl )- Alpha -oxy)-methyl-pyridine-carboxylic acid-(3) lactone and 3-( Alpha -(1''-methylpyrrol-(2'')-yl)- Alpha -(9''-ethylcarbazol-(3'')-yl)- Alpha -oxy )-methyl-pyridine-carboxylic acid-(2) lactone, an isomer mixture comprising 2-( Alpha -(acridin-(2'') -yl)-Alpha -(thianaphthen-(2'')-yl)- Alpha -oxy)-methyl-pyridine-carboxylic acid-(3) lactone and 3-( Alpha -(acridin-(2'')-yl)-Alpha -(thianaphthen-(2'')-yl) Alpha -oxy)-methyl-pyridine-carboxylic acid-(2) lactone, an isomer mixture comprising 2-( Alpha -(10''-methylphenothiazin-(3'')-yl)- Alpha -(1'',2''-dimethylindol-(3'')-yl)- Alpha -oxy)-methyl-pyridine-carboxylic acid-(3) lactone and 3-( Alpha -(10''-methylphenothiazin-(3'')-yl)- Alpha -(1'',2''-dimethylindol-(3'')-yl)- Alpha -oxy)-methyl-pyridine-carboxylic acid-(2) lactone, an isomer mixture comprising 2-( Alpha -(thiophen-(2'')-yl) Alpha -(1,'',2''-dimethylindol-(3'')-yl)- Alpha -oxy)-methyl-pYridine-carboxylic acid-(3) lactone and 3-( Alpha -(thiophen-(2'')-yl)-Alpha -(1'',2''-dimethyl-indol-(3'')-yl)- Alpha -oxy)-methyl-pyridine-carboxylic acid-(2) lactone, an isomer mixture comprising 2-( Alpha -(thianaphthen-(2'')-yl)-Alpha -(1'',2''-dimethylindol-(3'')-yl)- Alpha -oxy)-methyl-pyridine-carboxylic acid-(3) lactone and 3-( Alpha -(thianaphthen-(2'')-yl)- Alpha -(1'',2''-dimethylindol-(3'')-yl)-Alpha -oxy)-methyl-pyridine-carboxylic acid-(2) lactone, and an isomer -mixture comprising 2-( Alpha -(1'',2''-dimethylindol-(3'')-yl)- Alpha -(thiophen-(2'')-yl)- Alpha -oxy)-methyl-4-chloro-pyridine-carboxylic acid-(3) lactone and 3-( Alpha -(1'', 2''-dimethylindol-(3'')-yl)- Alpha -(thiophen-(2'')-yl)- Alpha -oxy)-methyl-4-chloro-pyridine-carboxylic acid-(2) lactone. 